A known inverter has the ability to control currents flowing through respective three-phase windings of a three-phase motor as an example of three-phase rotary machines. Specifically, a controller of the known inverter obtains actual values of at least first and second currents flowing through corresponding at least first and second phase windings of the three-phase motor using current sensors provided for the corresponding first and second phase windings. The controller also measures an actual rotational angle of a rotor of the three-phase motor using a rotational angle sensor. The known inverter is disclosed in Japanese Patent Application Publication No. 2013-118746, which will be referred to as a patent document 1.